Optical Gravitational Lensing Experiment Cepheids Have Lower Amplitudes in the Small Magellanic Cloud than in the Large Magellanic Cloud.
B Paczyński, B Pindor
Astrophys J | Published : 2000
We selected Cepheids from the Optical Gravitational Lensing Experiment database for the Magellanic Clouds in the period range of 101.1=P=101.4 days. There were 33 objects in the LMC and 35 in the SMC. We find that the median amplitude of Cepheids in the LMC is 18% larger than in the SMC, a 4 sigma effect. For a sample of 42 galactic Cepheids in the same period range, the median amplitude is 7% larger than in the LMC, suggesting that the higher the metal content the larger the amplitude. This implies that the period-flux amplitude relation is not universal and cannot be used to measure distances accurately, unless properly calibrated.